A conventional die to package interconnect architecture is illustrated in FIGS. 1–3 of the drawings. In the prior art semiconductor package 1, the interconnect scheme between die 2 and substrate 3 comprises copper bumps 4 which are electroplated on the die, and eutectic AgSn solder 5 which is paste printed on the substrate lands. Soldered joints are formed in the conventional process by placing the die with copper bumps and the substrate with contact lands or pads to which solder has been applied in contact with one another and heating the die and substrate together to a temperature higher than the solder melting temperature, followed by cooling the soldered assembly. The solder on the contact pads of the substrate is reflowed during this joining process to wet the copper standoffs on the die to form the soldered joints.
The die in the conventional package comprises thin film, inter layer dielectric (ILD) layers 6, see FIG. 4, on its front, lower surface under the copper bumps of the interconnect architecture. Due to the inherent weakness (cohesive and adhesive strengths) of the ILD material, stresses on the dielectric layers during reliability testing of the package can cause gross delamination of the ILD interfaces. A current focus for addressing the reliability issue posed by such ILD delamination in the die is on increasing the ILD material cohesive and adhesive strengths by modifying its chemistry, and by interface toughening schemes.
The ILD material that is typically used is carbon doped oxide. However, other ILD materials being evaluated for possible use are significantly weaker than the carbon doped oxide ILD material. Measurements on candidate materials indicate they are in some cases 10 to 100 times, e.g., at least about an order of magnitude, weaker than carbon doped oxide. These materials may be too weak to be accommodated in dies which are to be packaged using the current package-to-die interconnect architecture. An improved, low resistance package-to-die interconnect scheme for reducing die stresses would make it possible to use these significantly weaker ILD materials in the packaged die.